Adjustable bed frames to accommodate a plurality of spring-board and mattress widths are well known in the art. Typically, these bed frames consist of a pair of left and right side-rails disposed parallel to one another at a specified distance, a right pair of cross-bars joined to a right side-rail and a left pair of cross-bars joined to a left side-rail, and legs to support the assembled bed frame. The conventional construction of such a bed frame is from metal beam using an L-shaped cross-section wherein the vertical portion of the L-shaped cross-section projects upwardly to inhibit sideward misalignment of the box-spring, and the horizontal portion supports the weight of the box-spring and mattress. The use of metal beam has the benefit of providing adequate structural rigidity combined with moderate weight and cost.
The cross-bars are typically connected at one end to the side-rails at some specified distance from the head and the foot of the bed frame. Some designs incorporate a demountably slidable attachment for securing a cross-bar from one side-rail to a cross-bar from another side-rail along a length in which the cross-bars overlap. Such designs complicate warehouse inventory by necessitating sleeves and inserts that add weight, or increase the number of small parts needed for assembly. Other designs attach the cross-bar to the side-rail by means of a pin joint allowing the cross-bar to be rotatable with preferred pivot positions of approximately parallel to its connected side-rail for disassembled storage, and approximately perpendicular to its connected side-rail for assembled bed frame use. Commonly, the metal beam orientation of the cross-bar is opposite to the side-rail, with the cross-bar pin-mounted below the side-rail to enable free rotation of the cross-bar around the pivot pin joint. However, no automatic restriction to the rotation is provided in this configuration, so that the cross-bar may rotate a full 360.degree. around the pin joint, even though only a 90.degree. travel is typically required to achieve the preferred pivot positions.
The cross-bars from opposing left and right side-rails are generally connected to each other in such a manner that the right and left cross-bars at the head are demountably attached to each other, with a similar arrangement at the foot. Typically, the corresponding cross-bars are demountably attached by a slidable sleeve which is held in place by a removable friction element.
Cross-bars are typically designed to permit several positions at which a joined pair of cross-bars may be secured. Such a design feature enables a bed frame to be assembled so as to accommodate a number of established box-spring widths available on the market. The current market has available sizes such as single, twin, full, queen, cal-king and king. However, a bed frame which is wider than full-size may provide insufficient structural support to a box-spring and mattress in the absence of a reinforcement mechanism. Past solutions to provide additional support for queen- and king-size bed frames have incorporated a center-rail between the left and right side-rails with means to connect the center-rail to the cross-bars. However, even with this center-rail support, the mattress and bed-spring may be allowed to deflect significantly for a wide bed under the load of reclining persons. In addition, this mechanism for addressing adequate bed frame rigidity for wider beds increases the number of different parts on inventory that must be warehoused to satisfy consumer demand. Since warehouse space represents an additional cost in business, a reduction of redundant components would be desirable.
Furthermore, queen- and king-size box-springs and mattresses are generally longer than their twin- and full-size counterparts, and cal-king-size counterparts are longer still. Consequently, the addition of a center-rail to a shorter adjustable bed frame to accommodate a wider and longer box-spring and mattress leaves a cantilever of several inches. Consequently, when someone sits down on the unsupported end of a queen-size mattress lying on a width-expanded short bed frame, the load applied by the sitting person may produce a moment causing the box-spring to pivot on the end of the bed frame--upward at the head and downward at the foot, potentially causing the person sitting to unexpectedly fall off the bed.
Modern adjustable bed frames typically incorporate bed-legs for supporting the rails and cross-bars some distance above the floor. To facilitate locomotion of the assembled bed frame within a room, the legs often include wheels or castors at their bottom end. Other designs use a pad at the bed-leg bottom end to distribute the bed's weight across a wider area. In order to reduce the risk of a barefoot person approaching an assembled bed frame arranged for slumber from carelessly stubbing a toe on a bed-leg, the legs are attached inward from the side-rails. In the past, this feature has been satisfied by attaching the legs to the cross-bar. Aside from a restriction in mounting location flexibility, an additional risk is engendered from a lateral force applied to the bed-leg (such as from a person stubbing a toe) producing a moment from the pivot attachment between the cross-bar and the rail to thus loosen or even disconnect the cross-bar attached to the bed-leg from the opposite-side cross-bar.
The current adjustable bed frame designs require inventory of multiple types of parts to satisfy the existing variety of bed frame sizes, as well as impose other limitations, such as consumer safety and convenience. Hence, it would be desirable to overcome these restrictions to reduce inventory space requirements and increase flexibility in implementation.